In "Guero" as in "Pression" (1969/70) for cello or "Dal Niente" (1970) for clarinet Lachenmann was to re-invent the whole n ature of the instrument in response to a commission from Alfons Kontarsky. The performer scrapes along and over the white an d black keys (or both in combination) eventually progressing towards the strings thus producing six "manuals" each of whic h resembles the South American rasing percussion instrument.